Burner for reducing NOx emissions

Abstract

A burner for mixing and burning a gaseous fuel includes an inner pipe, carrying the gaseous fuel, and an outer pipe, carrying combustion air in the annular space between the inner and outer pipes. A cone-shaped horn is affixed to the end of the inner pipe. The horn extends near the inner surface of the outer pipe, leaving a narrow annular space therebetween. An alternating series of air jetting portions and blind portions around the periphery of the large end of the horn encourage the formation of mixing vortices as air passes through the air jetting portions. A plurality of radially directed fuel jetting openings in the inner pipe, upstream of the horn, inject gaseous fuel into the combustion air to form a lean air-fuel mixture. A plurality of jet openings at the end of the inner pipe, within the horn, direct gaseous fuel generally parallel to the diverging wall of the horn. Openings in the wall of the horn permit the entry of the lean mixture into the interior of the horn, where it mixes with the fuel flowing generally parallel to the wall of the horn. A spacial distribution, and a size distribution of the openings in the wall of the horn encourages the formation of a large number of generally independent flames, thereby encouraging stable combustion.

What is claimed is: 
     
       1. A burner comprising: an inner pipe;   an outer pipe concentrically disposed about said inner pipe, thereby forming an annular space between said inner pipe and said outer pipe;   a diverging horn affixed to an end of said inner pipe;   a first plurality of openings in said horn;   a second plurality of openings in said inner pipe, upstream of said horn;   said second plurality of openings being directed radially outward into said annular space;   a third plurality of openings in an end of said inner pipe within said horn;   said third plurality of openings being directed generally parallel to a wall of said horn; and   an alternating plurality of jetting portions and blind portions in an outer perimeter of said horn.   
     
     
       2. Apparatus according to claim 1, wherein said outer perimeter is slightly smaller than an inner diameter of said outer pipe, whereby an annular gap is formed therebetween. 
     
     
       3. Apparatus according to claim 1, wherein said first plurality of openings is unevenly distributed on said horn. 
     
     
       4. Apparatus according to claim 1, wherein said first plurality of openings have different sizes. 
     
     
       5. Apparatus according to claim 1, wherein said third plurality of openings are disposed in a vicinity of a narrow end of said horn. 
     
     
       6. Apparatus according to claim 5, wherein said first plurality of openings are completely absent in a vicinity of a wide end of said horn. 
     
     
       7. A burner comprising: an inner pipe;   an outer pipe concentrically disposed about said inner pipe and forming an annular space therebetween;   means for jetting a gaseous fuel from said inner pipe generally radially into said annular space;   a horn at an end of said inner pipe;   a gap between said horn and an inner surface of said outer pipe;   means for permitting a gas from said annular space to pass into an interior of said horn;   first means for jetting said gaseous fuel into said interior of said horn in a direction generally parallel to a wall of said horn; and   second means for jetting gas through an end wall of said horn.   
     
     
       8. Apparatus according to claim 7, wherein said end wall of said horn includes: an alternating series of jetting openings and blind portions about a perimeter of said horn; and   said jetting openings and blind portions being effective to form vortices downstream of said blind portions, whereby mixing of said gas with said gaseous fuel in enhanced, and stable combustion is aided.   
     
     
       9. A burner comprising: an outer pipe;   an inner pipe generally concentrically disposed within said outer pipe;   a generally conical horn affixed to an end of said inner pipe;   a gap between a wide end of said horn and an inner surface of said outer pipe;   means for producing a lean mixture of a fuel and air upstream of said horn;   means for permitting said lean mixture to pass through said gap;   a plurality of openings in said horn;   said plurality of openings being disposed in a vicinity of a narrow end of said horn;   said plurality of openings being absent in a vicinity of a wide end of said horn;   said plurality of openings permitting said lean mixture to pass therethrough; and   means for jetting a fuel from an end of said inner pipe within said horn, and generally parallel to a diverging inner surface of said horn.